The present invention generally relates to fuse cutouts used with power distribution systems as protective devices against electrical overload. In particular, the fuse cutout includes a mounting assembly, a pivotally movable fuseholder assembly received in the mounting assembly, and a fuse link held within the fuseholder that melts upon occurrence of an overload creating a fault interruption. The mounting assembly includes a top contact with a dome portion that frictionally engages the knurled outer surface of the fuseholder cap of the fuseholder assembly when the fuse cutout is operational. The frictional engagement ensures that the top contact and fuseholder cap remain in engagement prior to either the fuse link melting or the manual breaking of the fuse link by the link break lever.
The primary purpose of a fuse cutout is to provide protection for power distribution systems and the various apparatus on those power lines such as transformers and capacitor banks. An over current or electrical overload in the system can occur under various conditions, such as an animal or tree contacting the power lines or more than one power line contacting each other. The fuse cutout acts to interrupt the current, and then the fuseholder of the cutout xe2x80x9cdrops outxe2x80x9d, thereby preventing the voltage from being impressed across the fuseholder and providing a visual indication of operation to the utility line crew. Specifically, upon occurrence of an overload, the fuse link disposed within the fuseholder melts allowing the fuseholder to drop and interrupt the current.
Problems have occurred in conventional fuse cutouts when the fuseholder drops just prior to the fuse link melting. When the frictional engagement between the top contact of the mounting assembly and the fuseholder cap is not maintained, premature drop out results in catastrophic failure, flashover and damage to the fuse cutout. In addition, failure to interrupt an over current occurs in the conventional fuse cutouts when the fuseholder does not drop out, particularly after the fuse link has melting. Usually this occurs when the fuseholder cap gets stuck on the top contact preventing the fuseholder from pivoting to a drop out position.
Also, conventional fuse cutouts are susceptible to damage during operation, typically when a lineman forces the fuseholder closed with respect to the mounting assembly, thereby bending and damaging the fuse cutout. Moreover, the conventional fuse cutouts are also expensive to manufacture because the top contacts are formed of a thick copper alloy plate.
Examples of prior art fuse cutouts are disclosed in the following U.S. Pat. No.: 2,088,415 to Heinrich; U.S. Pat. No. 2,230,955 to Johnson; U.S. Pat. No. 2,324,888 to Strobel; U.S. Pat. No. 2,862,080 to Yonkers; U.S. Pat. No. 2,910,560 to Stroup et al.; U.S. Pat. No. 4,546,341 to McNaghten et al.; and U.S. Pat. No. 4,857,879 to Morgan.
Accordingly, an object of the present invention is to provide a fuse cutout that avoids catastrophic failure by preventing disengagement of the top contact and the fuseholder cap prior to the melting of the fuse link.
Another object of the present invention is to provide a fuse cutout that ensures consistent drop-out of the fuseholder upon the occurrence of an overload and the melting of the fuse link.
A further object of the present invention is to provide a fuse cutout that minimizes damage to the fuse cutout due to the opening and closing of the fuseholder.
A yet further object of the present invention is to provide a fuse cutout with a top contact that Is highly conductive and inexpensive to manufacture.
The foregoing objects are basically attained by a fuse cutout for connection to a power source comprising a mounting having upper and lower support members extending from opposing ends of the mounting, respectively. The upper support member includes a first contact extending therefrom. The first contact has opposing first and second end portions with the first end portion being attached to the upper support member, and a dome portion disposed between the first and second end portions. The dome portion includes opposing first and second dome surfaces and a first ridge extending along the second dome surface. A holder member is fixedly attached to the lower support member of the mounting. A pivot member is received in the holder member at a first pivot point, the pivot member being movable between first and second positions. A fuseholder is movable between closed and open positions and has upper and lower ends, the lower end being pivotally coupled to the pivot member at a second pivot point. The upper end has an engagement surface for engaging the first ridge of the dome portion of the first contact of the mounting forming an electrical connection therewith.
The foregoing objects are also obtained by a fuse cutout for connection to a power source comprising a mounting having upper and lower support members extending from opposing ends of the mounting, respectively. The upper support member includes a first contact extending therefrom. The first contact has opposing first and second contact surfaces, a first end portion attached to the upper support member, a second end portion opposite the first end, and a dome portion disposed between the first and second end portions. A holder member is fixedly attached to the lower support member of the mounting. A pivot member is received in the holder member at a first pivot point, the pivot member being movable between first and second positions. A fuseholder is movable between closed and open positions, and includes upper and lower ends. The lower end is pivotally coupled to the pivot member at a second pivot point. The upper end has a cap with opposing top and bottom portions and a middle portion extending therebetween, the top portion having a substantially knurled outer surface. The first and second positions of the pivot member correspond to the closed and open positions of the fuseholder, respectively. The knurled outer surface of the cap frictional engages the dome portion of the first contact when the fuseholder is in the closed position forming an electrical connection therewith.
By structuring the fuse cutout in this manner, failure of the cutout is avoided. In particular, the structure of the top contact and the fuseholder cap ensures both that the fuseholder does not drop prior to the melting of the fuse link and that it consistently drops after the link melts upon an occurrence of an overload.
Other objects, advantages and salient features of the invention will become apparent from the following detailed description which taken in conjunction with annexed drawings, discloses the preferred embodiment of the present invention.